I. Field of the Invention
This invention relates generally to electrosurgical instruments for grasping, coagulating and cutting tissue, and more particularly to an electrode configuration for a bipolar cutting/coagulating forceps that is designed to reduce tissue drag on the electrodes during cutting procedures.
II. Discussion of the Prior Art
A variety of electrosurgical instruments have been devised for carrying out various surgical procedures in which tissue needs to be cut and bleeding stemmed. Such electrosurgical devices typically include at least one conductive electrode. Radio frequency energy is conducted through this electrode to either a remote conductive body-plate (monopolar electrosurgery) or to a second, closely-space conductive electrode (bipolar). Current passing through the gap between the two electrodes will coagulate blood and other body fluids placed between those two electrodes.
Monopolar electrosurgical instruments suffer from the fact that the return path between the active electrode and the large area body-plate can be unpredictable as the electrical current seeks the return electrode through a path of least resistance. With bipolar electrosurgical instruments, however, because the two electrodes are closely spaced to one another, usually at the distal end of an instrument handle, the return path is very short and involves the tissue and fluids in the short path between the two electrodes.
In carrying out a surgical procedure, either open or endoscopic, a need often exists for an instrument that can readily cut through tissue and which can also be used to coagulate cut, bleeding blood vessels to promote hemostasis. It is desirable that these features be incorporated into a single instrument so that frequent instrument exchanges by the surgeon become unnecessary.
The Rydell et al. U.S. Pat. No. 5,514,134 describes a bipolar scissors designed for endoscopic use. This instrument mechanically cuts through tissue but includes bipolar electrodes for effecting coagulation. It includes a pair of blades that must be repeatedly opened and closed relative to one another as tissue is being cut in a scissors like action.
The Rydell U.S. Pat. No. 5,462,546 describes a hand-operable forceps instrument having two interfacing pivotal jaw members, each of which is an electrode. The jaw members can be made to meet to produce a pinching or gripping action on tissue and when the electrodes are energized, current is delivered through the jaws to the tissue to effect cauterization. That device, however, does not effectively cut tissue.
U.S. Pat. No. 5,342,381 to Tidemand describes an electrosurgical instrument that can be made to function both as a forceps for grasping and as a scissors for cutting. Again, cutting is only affected by manipulating a scissors handle to cause the blades to open and close in scissors-like fashion.
A need exists for a forceps-type instrument that can be used not only to grasp tissue but which embodies a feature whereby cutting can be achieved by drawing an edge of the instrument across tissue in scalpel-like fashion rather than snipping. While a monopolar instrument for cutting and grasping can readily be implemented, a problem arises when attempting to electrosurgically cut through tissue with a scalpel-like action using bipolar electrodes. For example, if the jaws of a forceps like that shown in the Rydell U.S. Pat. No. 5,258,006 were to be used to effect bipolar cutting, the jaws would have to be held slightly opened with respect to one another as the voltage is applied there across. As the slightly opened jaws are drawn across tissue, only one of the two jaws will be an active electrode, with the other serving as the indifferent or return electrode. Those skilled in the art appreciate that cutting only occurs at the active electrode and as the instrument is drawn across tissue to be cut, the inactive or indifferent electrode drags, making a smooth even cut more difficult. The present invention overcomes this problem.